1. Field of the Invention
The present invention relates generally to an apparatus and a method for compensating for a Transmission (Tx) gain in a wireless communication system, and more particularly, to an apparatus and a method for compensating for a Tx gain according to frequency and temperature changes in a transmitter of a wireless communication system.
2. Description of the Related Art
A Power Amplifier (PA) used in a transmitter of a wireless communication system may be controlled at various levels. For example, a three-level scheme may include high-level, mid-level, and low-level.
A gain of the PA varies according to a mode transition. Accordingly, a Tx Automatic Gain Control (AGC) adjusts the Tx gain using a Nonlinear Compensate Table (NCT) not to change a final Tx power of the PA.
Characteristics of the corresponding PA vary according to the temperature and the frequency. Hence, the transmitter according to the related art is required to update the NCT base on the changes of the temperature and the frequency. For example, the NCT has characteristics based on the temperature and frequency changes as shown in FIGS. 1A and 1B.
FIGS. 1A and 1B are graphs of the NCT characteristics according to the temperature and frequency change in the related art.
FIG. 1A depicts the NCT characteristics based on the frequency change, and FIG. 1B depicts the NCT characteristics based on the temperature change.
FIG. 1A depicts the NCT characteristics based on the frequency change using a Universal Mobile Telephony System (UMTS) Terrestrial Radio Access (UTRA) Absolute Radio Frequency Channel Number (UARFCN) sample of Table 1, among 277 channels in total, based on the band 1.
TABLE 1F0F1F2F3F496129675975098259888
As shown in Table 1, the PA cannot precisely control the power in the mid level 100 and the high level 110 according to the frequency change even by regulating the Tx gain using the NCT. Here, the ‘F’ indicates frequency.
FIG. 1B depicts the NCT characteristics at five temperatures of Table 2.
TABLE 2T0T1T2T3T4−20° C.0° C.20° C.40° C.60° C.
As shown in Table 2, the PA cannot precisely control the power in the mid level 120 and the high level 130 according to the temperature change even by regulating the Tx gain using the NCT. Here, the ‘T’ indicates temperature.
In this respect, systems according to the related art are unable to adjust the Tx gain according to the temperature and frequency change such that the final Tx power in the PA does not vary.